Charles-Augustin de Coulomb

Portrait by Hippolyte Lecomte

Born 14 June 1736Angoulme, Angoumois, France

Died 23 August 1806 (aged 70)Paris, France

Nationality French

Fields Physics

Known for Coulomb's law

Charles-Augustin de CoulombFrom Wikipedia, the free encyclopedia

Charles-Augustin de Coulomb (French: [kul ]; 14 June 1736 23 August 1806) was a French physicist.He was best known for developing Coulomb's law, the definition of the electrostatic force of attraction andrepulsion, but also did important work on friction. The SI unit of electric charge, the coulomb, was namedafter him.

Contents

1 Life2 Research3 See also4 References5 External links

Life

Charles Augustin de Coulomb was born in Angoulme in France. His parents were Henry Coulomb andCatherine Bajet. He went to school in the Collge Mazarin in Paris where his father lived. His studiesincluded philosophy, language and literature. He also received a good education in mathematics,astronomy, chemistry and botany.

Coulomb graduated in November 1761 from cole royale du gnie de Mzires. Over the next twentyyears, he was posted to a variety of locations where he was involved in engineering - structural,fortifications, soil mechanics, as well as other fields of engineering. His first posting was to Brest but inFebruary 1764 he was sent to Martinique, in the West Indies, where he was put in charge of building thenew Fort Bourbon and this task occupied him until June 1772.

On his return to France, Coulomb was sent to Bouchain. However, he now began to write important workson applied mechanics and he presented his first work to the Acadmie des Sciences in Paris in 1773. In1779 Coulomb was sent to Rochefort to collaborate with the Marquis de Montalembert in constructing afort made entirely from wood near Ile d'Aix. During his period at Rochefort, Coulomb carried on his research into mechanics, in particular using theshipyards in Rochefort as laboratories for his experiments.

Upon his return to France, with the rank of Captain, he was employed at La Rochelle, the Isle of Aix and Cherbourg. He discovered first an inverserelationship of the force between electric charges and the square of its distance and then the same relationship between magnetic poles. Later theserelationships were named after him as Coulomb's law.

In 1781, he was stationed at Paris. On the outbreak of the Revolution in 1789, he resigned his appointment as intendant des eaux et fontaines and retired to asmall estate which he possessed at Blois. He was recalled to Paris for a time in order to take part in the new determination of weights and measures, whichhad been decreed by the Revolutionary government. He became one of the first members of the French National Institute and was appointed inspector ofpublic instruction in 1802. His health was already very feeble and four years later he died in Paris.

Coulomb leaves a legacy as a pioneer in the field of geotechnical engineering for his contribution to retaining wall design. His name is one of the 72 namesinscribed on the Eiffel Tower.

Research

In 1784, his memoir Recherches thoriques et exprimentales sur la force de torsion et sur l'lasticit des fils de metal[1] (Theoretical research andexperimentation on torsion and the elasticity of metal wire) appeared. This memoir contained the results of Coulomb's experiments on the torsional force formetal wires. His general result is,

"... the moment of the torque is, for wires of the same metal, proportional to the torsional angle, the fourth power of the diameter and the inverse of thelength of the wire..."

In 1785, Coulomb presented his first three reports on Electricity and Magnetism:

- Premier Mmoire sur llectricit et le Magntisme.[2] In this publication, Coulomb describes "How to construct and use an electric balance (torsionbalance) based on the property of the metal wires of having a reaction torsion force proportional to the torsion angle." Coulomb also experimentallydetermined the law that explains how "two bodies electrified of the same kind of Electricity exert on each other." On page 574 he states:

Il rsulte donc de ces trois essais, que l'action rpulsive que les deux balles lectrifes de la mme nature d'lectricit exercent l'une surl'autre, suit la raison inverse du carr des distances.

Translation: It follows therefore from these three tests, that the repulsive force that the two balls -- [which were] electrified with the same kindof electricity -- exert on each other, follows the inverse proportion of the square of the distance.

Coulomb's torsion balance

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- Second Mmoire sur llectricit et le Magntisme.[3] In this publication, Coulomb carries out the "determinationaccording to which laws both the Magnetic and the Electric fluids act, either by repulsion or by attraction." On page 579,he states that the attractive force between two oppositely charged spheres is proportional to the product of the quantitiesof charge on the spheres and is inversely proportional to the square of the distance between the spheres.

- Troisime Mmoire sur llectricit et le Magntisme.[4] "On the quantity of Electricity that an isolated body loses in acertain time period, either by contact with less humid air or in the supports more or less idio-electric."

Four subsequent reports were published in the following years:

- Quatrime Mmoire[5] "Where two principal properties of the electric fluid are demonstrated: first, that this fluid doesnot expand into any object according to a chemical affinity or by an elective attraction, but that it divides itself betweendifferent objects brought into contact; second, that in conducting objects, the fluid, having achieved a state of stability,expands on the surface of the body and does not penetrate into the interior." (1786)

- Cinquime Mmoire[6] "On the manner in which the electric fluid divides itself between conducting objects broughtinto contact and the distribution of this fluid on the different parts of the surface of this object." (1787)

- Sixime Mmoire[7] "Continuation of research into the distribution of the electric fluid between several conductors. Determination of electric density atdifferent points on the surface of these bodies." (1788)

- Septime Mmoire[8] "On magnetism" (1789)

Coulomb explained the laws of attraction and repulsion between electric charges and magnetic poles, although he did not find any relationship between thetwo phenomena. He thought that the attraction and repulsion were due to different kinds of fluids. Charles de Coulomb was the one who discoveredCoulombs Law; he did this by measuring the twist in a wire, or Torsion Balance.

See also

Coulomb frictionMohr-Coulomb theory

ReferencesCoulomb (1784) "Recherches thoriques et exprimentales sur la force de torsion et sur l'lasticit des fils de metal," (http://books.google.com/books?id=SS5EAAAAcAAJ&pg=PA229#v=onepage&q&f=false) Histoire de lAcadmie Royale des Sciences, pages 229-269.

1.

Coulomb (1785a) "Premier mmoire sur llectricit et le magntisme," (http://books.google.com/books?id=by5EAAAAcAAJ&pg=PA569#v=onepage&q&f=false)Histoire de lAcadmie Royale des Sciences, pages 569-577.

2.

Coulomb (1785b) "Second mmoire sur llectricit et le magntisme," (http://books.google.com/books?id=by5EAAAAcAAJ&pg=PA578#v=onepage&q&f=false)Histoire de lAcadmie Royale des Sciences, pages 578-611.

3.

Coulomb (1785c) "Troisime mmoire sur llectricit et le magntisme," (http://books.google.com/books?id=by5EAAAAcAAJ&pg=PA612#v=onepage&q&f=false) Histoire de lAcadmie Royale des Sciences, pages 612-638.

4.

Coulomb (1786) "Quatrime mmoire sur llectricit," (http://books.google.com/books?id=5hAVAAAAQAAJ&pg=RA1-PA67#v=onepage&q&f=false) Histoire delAcadmie Royale des Sciences, pages 67-77.

5.

Coulomb (1787) "Cinquime mmoire sur llectricit," (http://books.google.com/books?id=0uIEAAAAQAAJ&pg=PA421#v=onepage&q&f=false) Histoire delAcadmie Royale des Sciences, pages 421-467.

6.

Coulomb (1788) "Sixime mmoire sur llectricit," (http://books.google.com/books?id=my5EAAAAcAAJ&pg=PA619#v=onepage&q&f=false) Histoire delAcadmie Royale des Sciences, pages 617-705.

7.

Coulomb (1789) "Septime mmoire sur llectricit et le magntisme," (http://books.google.com/books?id=XhEVAAAAQAAJ&pg=PA455#v=onepage&q&f=false)Histoire de lAcadmie Royale des Sciences, pages 455-505.

8.

This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopdia Britannica (11th ed.).Cambridge University Press.

External links

Thorie des machines simples (http://books.google.com/books?id=zGYSAAAAIAAJ&printsec=frontcover&dq=Charles+de+coulomb&as_brr=1#PPR3,M2) (1821)Collection de mmoires relatifs la physique (http://books.google.com/books?id=w0EAAAAAQAAJ&pg=PR8&dq=Charles+de+coulomb&as_brr=1#PPR2,M2) (1884)French National Library (http://cnum.cnam.fr/CGI/fpage.cgi?8CA121-1/3/100/416/79/316) The Mmoires ofCoulomb available in pdf format.O'Connor, John J.; Robertson, Edmund F., "Charles-Augustin de Coulomb" (http://www-history.mcs.st-andrews.ac.uk/Biographies/Coulomb.html), MacTutor History of Mathematics archive, University of StAndrews.

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Categories: 1736 births 1806 deaths People from Angoulme University of Paris alumni French physicistsGeotechnical engineers French civil engineers French Roman CatholicsMembers of the French Academy of Sciences

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